The present invention relates to an electronic device, and particularly to a sealing structure for various sensors for outputting various physical quantities as electrical signals by a sensing element for detecting various physical quantities. The invention also relates to an electronic circuit for controlling the sensing element installed in an engine compartment and to a mounting structure with improved corrosion resistance, for mounting an electronic circuit of an electronic device in a vehicle, said electronic device having a microprocessor for controlling various states of the vehicle upon receipt of electrical signals of the aforementioned various sensors.
Various kinds of known hybrid IC substrates have a thick film resistor printed on a ceramic substrate and include parts such as a semiconductor integrated circuit, a capacitor, and a diode. For a hybrid IC substrate having conductor wires of silver, silver alloy, copper, or copper alloy, (particularly for a hybrid IC substrate adopted in an electronic device for car use), corrosion of the conductor wires due to corrosive gas is a concern, and as a corrosion improvement measure, coating the conductor wires with glass is considered.
However, the resistors printed on a hybrid IC substrate and the mounted electronic parts are varied, and to provide a highly precise electronic device, the resistance and characteristics must be adjusted. For that purpose, an exposed conductor part is required. As a method for covering the exposed part, soldering is generally used.
However, it is a method in consideration of contact at the time of probing instead of a target of improving the corrosion resistance, which is limited to a case necessary for probing. Further, even when soldering is adopted, there are many exposed parts of the conductor wires due to poor wettability of solder.
As an improvement measure for solder wettability, as described in Japanese Laid-Open Patent Publication No. Hei 04-334083, an improving method by a process such as two-dimensional calcination is adopted.